1. Field of the Invention
This invention relates generally to connections for scaffolding and, more particularly, to latchable scaffolding connections between horizontal and vertical scaffold members.
2. Background of the Invention
Many different designs have been employed to secure the ends of horizontal scaffold members to vertical scaffold members. Because of a concern for a positive locking arrangement, prior art connections employ a latch assembly, whereby the connection between a horizontal and a vertical member is held in place against an uplifting force by some type of latch. One such joint is disclosed in U.S. Pat. No. 4,445,307, which discloses a connector positioned on a horizontal scaffold member, where the connector has two vertically spaced hook sections. These hook sections couple with two vertically spaced upstanding ring members located on the vertical scaffold member. To withstand an uplifting force, the connector includes a wedge that is driven (generally by a hammer) into position below the upper ring member, thereby latching the connector hook sections against the ring member through a wedging type of action.
A second type of latching connector is disclosed in U.S. Pat. Nos. 5,078,532 and 5,028,164, hereby incorporated by reference. These patents also show a connector positioned on a horizontal scaffold member, where the connector has two vertically spaced hooked sections that couple with two vertically spaced upstanding ring members located on the vertical scaffold member. In this device, the latching of the ring members to the hooked sections is accomplished by a deploying a pivoting member, positioned on the connector, into position below the top ring member. The pivoting member cages or traps the connector to the vertical member, thereby resisting an uplifting force. The pivoting member allows for ease of assembly of a scaffold structure, and the assembled joint retains a degree of play, as this connector lacks the wedging action of the '307 patented device.
By using a two points of attachment between a horizontal and vertical member (the two hooked sections coupled to the two upstanding ring members), the '532 join and the '307 join are more resistive to torsional forces than would be a single ring/hook section embodiment, such as shown in U.S. Pat. No. 4,369,859. However, because the bottom hook of the '532 connector and '307 connector is not latched to the bottom ring member, the connector is still weak when subject to high torsional forces; for instance, it is not recommended that a worker tie onto a horizontal member that is designed only as specified in the '532 patent, as a falling worker will subject that connector to high torsional force and possible connector failure. Hence it is desired to have a scaffold join that is more resistive to torsional forces, that enables a scaffold structure to be easily and quickly erected, and can be used with existing vertical scaffold members.